A New Mechanism for Maunder-like Solar Minima: Phase Synchronization Dynamics in a Simple Nonlinear Oscillator of Magnetohydrodynamic Rossby Waves

The long-term solar cycle variability and Grand solar minima remain open questions from a theoretical point of view. Recently, a growing basis of evidence points out to the role of the magnetic Rossby waves in the solar cycle. Here we present a simple deterministic model, based on a low-order spectral representation of the barotropic quasi-geostrophic-magnetohydrodynamic equations for the Solar tachocline. This model supports the idea of the long-term behavior of the solar activity as a result of nonlinear interaction of magnetic Rossby modes. Solutions show that Rossby waves undergo irregular switches between periods of high activity and periods of suppressed activity, resembling the Maunder minimum. Low-energy states in the model are associated with the synchronization of the dynamical phases of the waves. These irregular transitions in the amplitudes of the waves are reminiscent of the observed time series of the solar activity. This suggests that Maunder-like states arise from chaotic transitions between regimes with different degrees of organization in the system.